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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 277 (1985), S. 484-488 
    ISSN: 1432-069X
    Keywords: Mechanical properties ; Repeated strain in vivo ; Time dependence of recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A new method was developed to study the in vivo recovery of mechanical properties of rat skin after repeated strain. Full recovery, i.e., restitutio ad integrum, can be observed only in in vivo experiments but not in in vitro conditions. For the in vivo studies, tabs were fastened on the back skin of rats to test stress-strain behaviour both perpendicular and longitudinal to the body axis. Under anesthesia, skin was extended repeatedly 30 times to an elongation of up to 50% of the distance between the tabs. The experiment was repeated in the same animals at either 0.5, 1, 6, or 16 h. Differences depending on the direction of stretching versus body axis were observed during the first run. A decrease in stress values depending on the logarithm of the number of cycles was found, in both directions, to be attributable to the relaxation phenomenon. The measured stress values after 0.5, 1, and 6 h were considerably lower compared to the first run, thus indicating an incomplete recovery. After 16 h, an almost complete recovery was observed, so that, in perpendicular samples, even higher values were observed, thus indicating an overshooting of the repair mechanisms. The difficulties associated with obtaining appropriate physical and mathematical models for the mechanical properties of skin are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 244 (1972), S. 130-134 
    ISSN: 1432-069X
    Keywords: Cutis ; Corium ; Epidermis ; Mechanical properties ; In vivo ; In vitro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 262 (1978), S. 15-25 
    ISSN: 1432-069X
    Keywords: Repeated UV-irradiation ; Skin ; Hairless mouse ; Mechanical properties ; Collagen ; Elastin ; Wiederholte UV-Bestrahlung ; Haut ; Haarlose Maus ; Mechanische Eigenschaften ; Collagen ; Elastin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An der Haut von haarlosen Mäusen wurde die Wirkung von wiederholter UV-Bestrahlung auf mechanische und biochemische Parameter untersucht. Eine tägliche UV-A-Bestrahlung über 1 h während 8 Wochen verursachte nur eine leichte Zunahme der Hautdicke und eine Abnahme der Dehnung beim Abriß. Nach UV-B- bzw. UV-C-Bestrahlung waren die Veränderungen jedoch sehr viel drastischer. In diesen Untersuchungsreihen wurden die Mäuse mit einer UV-Lampe im Abstand von 17 cm bestrahlt, so daß die Bestrahlungsintensität 20 mW/cm2 UV-B und-A und 14 mW/cm2 UV-C betrug. Über 1–6 Wochen wurden verschiedene Tiergruppen täglich 15–90 s exponiert. Die Reißkraft, die Reißfestigkeit und der Elastizitätsmodul zeigten nach mittleren Strahlendosen nach 1–2 Wochen eine Zunahme, jedoch nach hohen Strahlendosen und langdauernder Behandlung eine Abnahme. Die Dehnung beim Abriß war der empfindlichste Parameter insofern, als er in Abhängigkeit von Expositionszeit und Behandlungsdauer abnahm. Der Gehalt an unlöslichem Kollagen und Gesamtkollagen war nach langdauernder Behandlung vermindert und demnach mit den mechanischen Parametern korreliert. Der Elastin-Gehalt wurde nur gering beeinflußt und war somit mit den mechanischen Meßwerten nicht korreliert. In diesen Experimenten konnte ein günstiger Effekt einer kurzdauernden Behandlung mit niedrigen UV-Bestrahlungsdosen auf die mechanischen Eigenschaften der Haut gezeigt werden. Eine langdauernde Behandlung mit hohen Dosen von UV-B bewirkte jedoch ungünstige Effekte, wobei hauptsächlich die Dehnung beim Abriß, aber auch die Reißfestigkeit und der Elastizitätsmodul vermindert waren.
    Notes: Summary The effect of repeated UV-irradiation on mechanical and biochemical parameters was studied in skin of hairless mice. UV-A irradiation for a period of 1 h daily over 8 weeks caused only a slight increase in skin thickness and a decrease in ultimate strain. The changes induced by UV-B and C, however, were quite remarkable. Skin thickness was increased depending on the daily dose exposure time (15–90 s at an irradiation rate of 20 mW/cm2 UV-B and A and of 14 mW/cm2 UV-C) and the duration of treatment (1–6 weeks). Ultimated load, tensile strength and modulus of elasticity showed an increase following medium dosages after 1 and 2 weeks, however, a decrease after high dosages and longterm treatment. Ultimate strain was found to be the most sensitive parameter being decreased depending on exposure time and duration of treatment. Insoluble collagen and total collagen were decreased after long-term treatment thus being correlated with the mechanical parameters. The elastin content was only barely influenced and not correlated with the mechanical data, e.g. the modulus of elasticity. Thus, a favourable effect of short-term treatment with low doses of UV-irradiation of mechanical parameters of skin could be demonstrated. Long-term treatment with relatively high doses of UV-B, however, resulted in unfavourable effects, whereby first ultimate strain, then ultimate load, modulus of elasticity and tensile strength were decreased.
    Type of Medium: Electronic Resource
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